follow_track.hpp

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/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */
 
#ifndef  FOLLOW_TRACK_HPP
#define  FOLLOW_TRACK_HPP
 
#include "../pbs.h"
#include "../roadveh.h"
#include "../station_base.h"
#include "../train.h"
#include "../tunnelbridge.h"
#include "../tunnelbridge_map.h"
#include "../depot_map.h"
#include "pathfinder_func.h"
 
template <TransportType Ttr_type_, typename VehicleType, bool T90deg_turns_allowed_ = true, bool Tmask_reserved_tracks = false>
struct CFollowTrackT
{
  enum ErrorCode {
    EC_NONE,
    EC_OWNER,
    EC_RAIL_ROAD_TYPE,
    EC_90DEG,
    EC_NO_WAY,
    EC_RESERVED,
  };
 
  const VehicleType  *m_veh;           
  Owner               m_veh_owner;     
  TileIndex           m_old_tile;      
  Trackdir            m_old_td;        
  TileIndex           m_new_tile;      
  TrackdirBits        m_new_td_bits;   
  DiagDirection       m_exitdir;       
  bool                m_is_tunnel;     
  bool                m_is_bridge;     
  bool                m_is_station;    
  int                 m_tiles_skipped; 
  ErrorCode           m_err;
  RailTypes           m_railtypes;
 
  inline CFollowTrackT(const VehicleType *v = nullptr, RailTypes railtype_override = INVALID_RAILTYPES)
  {
    Init(v, railtype_override);
  }
 
  inline CFollowTrackT(Owner o, RailTypes railtype_override = INVALID_RAILTYPES)
  {
    assert(IsRailTT());
    m_veh = nullptr;
    Init(o, railtype_override);
  }
 
  inline void Init(const VehicleType *v, RailTypes railtype_override)
  {
    assert(!IsRailTT() || (v != nullptr && v->type == VEH_TRAIN));
    m_veh = v;
    Init(v != nullptr ? v->owner : INVALID_OWNER, IsRailTT() && railtype_override == INVALID_RAILTYPES ? Train::From(v)->compatible_railtypes : railtype_override);
  }
 
  inline void Init(Owner o, RailTypes railtype_override)
  {
    assert(!IsRoadTT() || m_veh != nullptr);
    assert(!IsRailTT() || railtype_override != INVALID_RAILTYPES);
    m_veh_owner = o;
    /* don't worry, all is inlined so compiler should remove unnecessary initializations */
    m_old_tile = INVALID_TILE;
    m_old_td = INVALID_TRACKDIR;
    m_new_tile = INVALID_TILE;
    m_new_td_bits = TRACKDIR_BIT_NONE;
    m_exitdir = INVALID_DIAGDIR;
    m_is_station = m_is_bridge = m_is_tunnel = false;
    m_tiles_skipped = 0;
    m_err = EC_NONE;
    m_railtypes = railtype_override;
  }
 
  debug_inline static TransportType TT() { return Ttr_type_; }
  debug_inline static bool IsWaterTT() { return TT() == TRANSPORT_WATER; }
  debug_inline static bool IsRailTT() { return TT() == TRANSPORT_RAIL; }
  inline bool IsTram() { return IsRoadTT() && RoadTypeIsTram(RoadVehicle::From(m_veh)->roadtype); }
  debug_inline static bool IsRoadTT() { return TT() == TRANSPORT_ROAD; }
  inline static bool Allow90degTurns() { return T90deg_turns_allowed_; }
  inline static bool DoTrackMasking() { return Tmask_reserved_tracks; }
 
  inline DiagDirection GetSingleTramBit(TileIndex tile)
  {
    assert(IsTram()); // this function shouldn't be called in other cases
 
    if (IsNormalRoadTile(tile)) {
      RoadBits rb = GetRoadBits(tile, RTT_TRAM);
      switch (rb) {
        case ROAD_NW: return DIAGDIR_NW;
        case ROAD_SW: return DIAGDIR_SW;
        case ROAD_SE: return DIAGDIR_SE;
        case ROAD_NE: return DIAGDIR_NE;
        default: break;
      }
    }
    return INVALID_DIAGDIR;
  }
 
  inline bool Follow(TileIndex old_tile, Trackdir old_td)
  {
    m_old_tile = old_tile;
    m_old_td = old_td;
    m_err = EC_NONE;
 
    assert([&]() {
      if (IsTram() && GetSingleTramBit(m_old_tile) != INVALID_DIAGDIR) return true; // Skip the check for single tram bits
      const uint sub_mode = (IsRoadTT() && m_veh != nullptr) ? (this->IsTram() ? RTT_TRAM : RTT_ROAD) : 0;
      const TrackdirBits old_tile_valid_dirs = TrackStatusToTrackdirBits(GetTileTrackStatus(m_old_tile, TT(), sub_mode));
      return (old_tile_valid_dirs & TrackdirToTrackdirBits(m_old_td)) != TRACKDIR_BIT_NONE;
    }());
 
    m_exitdir = TrackdirToExitdir(m_old_td);
    if (ForcedReverse()) return true;
    if (!CanExitOldTile()) return false;
    FollowTileExit();
    if (!QueryNewTileTrackStatus()) return TryReverse();
    m_new_td_bits &= DiagdirReachesTrackdirs(m_exitdir);
    if (m_new_td_bits == TRACKDIR_BIT_NONE || !CanEnterNewTile()) {
      /* In case we can't enter the next tile, but are
       * a normal road vehicle, then we can actually
       * try to reverse as this is the end of the road.
       * Trams can only turn on the appropriate bits in
       * which case reaching this would mean a dead end
       * near a building and in that case there would
       * a "false" QueryNewTileTrackStatus result and
       * as such reversing is already tried. The fact
       * that function failed can have to do with a
       * missing road bit, or inability to connect the
       * different bits due to slopes. */
      if (IsRoadTT() && !IsTram() && TryReverse()) return true;
 
      /* CanEnterNewTile already set a reason.
       * Do NOT overwrite it (important for example for EC_RAIL_ROAD_TYPE).
       * Only set a reason if CanEnterNewTile was not called */
      if (m_new_td_bits == TRACKDIR_BIT_NONE) m_err = EC_NO_WAY;
 
      return false;
    }
    if ((!IsRailTT() && !Allow90degTurns()) || (IsRailTT() && Rail90DegTurnDisallowed(GetTileRailType(m_old_tile), GetTileRailType(m_new_tile), !Allow90degTurns()))) {
      m_new_td_bits &= (TrackdirBits)~(int)TrackdirCrossesTrackdirs(m_old_td);
      if (m_new_td_bits == TRACKDIR_BIT_NONE) {
        m_err = EC_90DEG;
        return false;
      }
    }
    return true;
  }
 
  inline bool MaskReservedTracks()
  {
    if (!DoTrackMasking()) return true;
 
    if (m_is_station) {
      /* Check skipped station tiles as well. */
      TileIndexDiff diff = TileOffsByDiagDir(m_exitdir);
      for (TileIndex tile = m_new_tile - diff * m_tiles_skipped; tile != m_new_tile; tile += diff) {
        if (HasStationReservation(tile)) {
          m_new_td_bits = TRACKDIR_BIT_NONE;
          m_err = EC_RESERVED;
          return false;
        }
      }
    }
 
    TrackBits reserved = GetReservedTrackbits(m_new_tile);
    /* Mask already reserved trackdirs. */
    m_new_td_bits &= ~TrackBitsToTrackdirBits(reserved);
    /* Mask out all trackdirs that conflict with the reservation. */
    for (Track t : SetTrackBitIterator(TrackdirBitsToTrackBits(m_new_td_bits))) {
      if (TracksOverlap(reserved | TrackToTrackBits(t))) m_new_td_bits &= ~TrackToTrackdirBits(t);
    }
    if (m_new_td_bits == TRACKDIR_BIT_NONE) {
      m_err = EC_RESERVED;
      return false;
    }
    return true;
  }
 
protected:
  inline void FollowTileExit()
  {
    m_is_station = m_is_bridge = m_is_tunnel = false;
    m_tiles_skipped = 0;
 
    /* extra handling for tunnels and bridges in our direction */
    if (IsTileType(m_old_tile, MP_TUNNELBRIDGE)) {
      DiagDirection enterdir = GetTunnelBridgeDirection(m_old_tile);
      if (enterdir == m_exitdir) {
        /* we are entering the tunnel / bridge */
        if (IsTunnel(m_old_tile)) {
          m_is_tunnel = true;
          m_new_tile = GetOtherTunnelEnd(m_old_tile);
        } else { // IsBridge(m_old_tile)
          m_is_bridge = true;
          m_new_tile = GetOtherBridgeEnd(m_old_tile);
        }
        m_tiles_skipped = GetTunnelBridgeLength(m_new_tile, m_old_tile);
        return;
      }
      assert(ReverseDiagDir(enterdir) == m_exitdir);
    }
 
    /* normal or station tile, do one step */
    m_new_tile = TileAddByDiagDir(m_old_tile, m_exitdir);
 
    /* special handling for stations */
    if (IsRailTT() && HasStationTileRail(m_new_tile)) {
      m_is_station = true;
    } else if (IsRoadTT() && IsStationRoadStopTile(m_new_tile)) {
      m_is_station = true;
    }
  }
 
  inline bool QueryNewTileTrackStatus()
  {
    if (IsRailTT() && IsPlainRailTile(m_new_tile)) {
      m_new_td_bits = (TrackdirBits)(GetTrackBits(m_new_tile) * 0x101);
    } else if (IsRoadTT()) {
      m_new_td_bits = GetTrackdirBitsForRoad(m_new_tile, this->IsTram() ? RTT_TRAM : RTT_ROAD);
    } else {
      m_new_td_bits = TrackStatusToTrackdirBits(GetTileTrackStatus(m_new_tile, TT(), 0));
    }
    return (m_new_td_bits != TRACKDIR_BIT_NONE);
  }
 
  inline bool CanExitOldTile()
  {
    /* road stop can be left at one direction only unless it's a drive-through stop */
    if (IsRoadTT() && IsBayRoadStopTile(m_old_tile)) {
      DiagDirection exitdir = GetRoadStopDir(m_old_tile);
      if (exitdir != m_exitdir) {
        m_err = EC_NO_WAY;
        return false;
      }
    }
 
    /* single tram bits can only be left in one direction */
    if (IsTram()) {
      DiagDirection single_tram = GetSingleTramBit(m_old_tile);
      if (single_tram != INVALID_DIAGDIR && single_tram != m_exitdir) {
        m_err = EC_NO_WAY;
        return false;
      }
    }
 
    /* road depots can be also left in one direction only */
    if (IsRoadTT() && IsDepotTypeTile(m_old_tile, TT())) {
      DiagDirection exitdir = GetRoadDepotDirection(m_old_tile);
      if (exitdir != m_exitdir) {
        m_err = EC_NO_WAY;
        return false;
      }
    }
    return true;
  }
 
  inline bool CanEnterNewTile()
  {
    if (IsRoadTT() && IsBayRoadStopTile(m_new_tile)) {
      /* road stop can be entered from one direction only unless it's a drive-through stop */
      DiagDirection exitdir = GetRoadStopDir(m_new_tile);
      if (ReverseDiagDir(exitdir) != m_exitdir) {
        m_err = EC_NO_WAY;
        return false;
      }
    }
 
    /* single tram bits can only be entered from one direction */
    if (IsTram()) {
      DiagDirection single_tram = GetSingleTramBit(m_new_tile);
      if (single_tram != INVALID_DIAGDIR && single_tram != ReverseDiagDir(m_exitdir)) {
        m_err = EC_NO_WAY;
        return false;
      }
    }
 
    /* road and rail depots can also be entered from one direction only */
    if (IsRoadTT() && IsDepotTypeTile(m_new_tile, TT())) {
      DiagDirection exitdir = GetRoadDepotDirection(m_new_tile);
      if (ReverseDiagDir(exitdir) != m_exitdir) {
        m_err = EC_NO_WAY;
        return false;
      }
      /* don't try to enter other company's depots */
      if (GetTileOwner(m_new_tile) != m_veh_owner) {
        m_err = EC_OWNER;
        return false;
      }
    }
    if (IsRailTT() && IsDepotTypeTile(m_new_tile, TT())) {
      DiagDirection exitdir = GetRailDepotDirection(m_new_tile);
      if (ReverseDiagDir(exitdir) != m_exitdir) {
        m_err = EC_NO_WAY;
        return false;
      }
    }
 
    /* rail transport is possible only on tiles with the same owner as vehicle */
    if (IsRailTT() && GetTileOwner(m_new_tile) != m_veh_owner) {
      /* different owner */
      m_err = EC_NO_WAY;
      return false;
    }
 
    /* rail transport is possible only on compatible rail types */
    if (IsRailTT()) {
      RailType rail_type = GetTileRailType(m_new_tile);
      if (!HasBit(m_railtypes, rail_type)) {
        /* incompatible rail type */
        m_err = EC_RAIL_ROAD_TYPE;
        return false;
      }
    }
 
    /* road transport is possible only on compatible road types */
    if (IsRoadTT()) {
      const RoadVehicle *v = RoadVehicle::From(m_veh);
      RoadType roadtype = GetRoadType(m_new_tile, GetRoadTramType(v->roadtype));
      if (!HasBit(v->compatible_roadtypes, roadtype)) {
        /* incompatible road type */
        m_err = EC_RAIL_ROAD_TYPE;
        return false;
      }
    }
 
    /* tunnel holes and bridge ramps can be entered only from proper direction */
    if (IsTileType(m_new_tile, MP_TUNNELBRIDGE)) {
      if (IsTunnel(m_new_tile)) {
        if (!m_is_tunnel) {
          DiagDirection tunnel_enterdir = GetTunnelBridgeDirection(m_new_tile);
          if (tunnel_enterdir != m_exitdir) {
            m_err = EC_NO_WAY;
            return false;
          }
        }
      } else { // IsBridge(m_new_tile)
        if (!m_is_bridge) {
          DiagDirection ramp_enderdir = GetTunnelBridgeDirection(m_new_tile);
          if (ramp_enderdir != m_exitdir) {
            m_err = EC_NO_WAY;
            return false;
          }
        }
      }
    }
 
    /* special handling for rail stations - get to the end of platform */
    if (IsRailTT() && m_is_station) {
      /* entered railway station
       * get platform length */
      uint length = BaseStation::GetByTile(m_new_tile)->GetPlatformLength(m_new_tile, TrackdirToExitdir(m_old_td));
      /* how big step we must do to get to the last platform tile? */
      m_tiles_skipped = length - 1;
      /* move to the platform end */
      TileIndexDiff diff = TileOffsByDiagDir(m_exitdir);
      diff *= m_tiles_skipped;
      m_new_tile = TileAdd(m_new_tile, diff);
      return true;
    }
 
    return true;
  }
 
  inline bool ForcedReverse()
  {
    /* rail and road depots cause reversing */
    if (!IsWaterTT() && IsDepotTypeTile(m_old_tile, TT())) {
      DiagDirection exitdir = IsRailTT() ? GetRailDepotDirection(m_old_tile) : GetRoadDepotDirection(m_old_tile);
      if (exitdir != m_exitdir) {
        /* reverse */
        m_new_tile = m_old_tile;
        m_new_td_bits = TrackdirToTrackdirBits(ReverseTrackdir(m_old_td));
        m_exitdir = exitdir;
        m_tiles_skipped = 0;
        m_is_tunnel = m_is_bridge = m_is_station = false;
        return true;
      }
    }
 
    /* Single tram bits and standard road stops cause reversing. */
    if (IsRoadTT() && ((IsTram() && GetSingleTramBit(m_old_tile) == ReverseDiagDir(m_exitdir)) ||
        (IsBayRoadStopTile(m_old_tile) && GetRoadStopDir(m_old_tile) == ReverseDiagDir(m_exitdir)))) {
      /* reverse */
      m_new_tile = m_old_tile;
      m_new_td_bits = TrackdirToTrackdirBits(ReverseTrackdir(m_old_td));
      m_exitdir = ReverseDiagDir(m_exitdir);
      m_tiles_skipped = 0;
      m_is_tunnel = m_is_bridge = m_is_station = false;
      return true;
    }
 
    return false;
  }
 
  inline bool TryReverse()
  {
    if (IsRoadTT() && !IsTram()) {
      /* if we reached the end of road, we can reverse the RV and continue moving */
      m_exitdir = ReverseDiagDir(m_exitdir);
      /* new tile will be the same as old one */
      m_new_tile = m_old_tile;
      /* set new trackdir bits to all reachable trackdirs */
      QueryNewTileTrackStatus();
      m_new_td_bits &= DiagdirReachesTrackdirs(m_exitdir);
      if (m_new_td_bits != TRACKDIR_BIT_NONE) {
        /* we have some trackdirs reachable after reversal */
        return true;
      }
    }
    m_err = EC_NO_WAY;
    return false;
  }
 
public:
  int GetSpeedLimit(int *pmin_speed = nullptr) const
  {
    int min_speed = 0;
    int max_speed = INT_MAX; // no limit
 
    /* Check for on-bridge speed limit */
    if (!IsWaterTT() && IsBridgeTile(m_old_tile)) {
      int spd = GetBridgeSpec(GetBridgeType(m_old_tile))->speed;
      if (IsRoadTT()) spd *= 2;
      max_speed = std::min(max_speed, spd);
    }
    /* Check for speed limit imposed by railtype */
    if (IsRailTT()) {
      uint16_t rail_speed = GetRailTypeInfo(GetRailType(m_old_tile))->max_speed;
      if (rail_speed > 0) max_speed = std::min<int>(max_speed, rail_speed);
    }
    if (IsRoadTT()) {
      /* max_speed is already in roadvehicle units, no need to further modify (divide by 2) */
      uint16_t road_speed = GetRoadTypeInfo(GetRoadType(m_old_tile, GetRoadTramType(RoadVehicle::From(m_veh)->roadtype)))->max_speed;
      if (road_speed > 0) max_speed = std::min<int>(max_speed, road_speed);
    }
 
    /* if min speed was requested, return it */
    if (pmin_speed != nullptr) *pmin_speed = min_speed;
    return max_speed;
  }
};
 
typedef CFollowTrackT<TRANSPORT_WATER, Ship,        true > CFollowTrackWater;
typedef CFollowTrackT<TRANSPORT_ROAD,  RoadVehicle, true > CFollowTrackRoad;
typedef CFollowTrackT<TRANSPORT_RAIL,  Train,       true > CFollowTrackRail;
 
typedef CFollowTrackT<TRANSPORT_RAIL,  Train,       false> CFollowTrackRailNo90;
 
typedef CFollowTrackT<TRANSPORT_RAIL, Train, true,  true > CFollowTrackFreeRail;
typedef CFollowTrackT<TRANSPORT_RAIL, Train, false, true > CFollowTrackFreeRailNo90;
 
#endif /* FOLLOW_TRACK_HPP */